IF you only want Products with price > 15 in your app, you do a "Where Clause" in your script.
IF you want all Products in your app but only show some of them in a table, you can solve this in many ways.
One solution is to create a field in your script called [Price >15]
if (Price>15, 'yes','no') as [Price >15]
Then in your app on the sheet next to your table of Products, you create a listbox of this field.
A final solution, would be to do nothing in the script, and instead do everything in the app and its expressions usung Set Analysis. You can find many examples in this forum about Set Analysis.
Svebeck Consulting AB
As Robert said, for the first option (load only the products with price > 15) you should use something like this in your script:
(ooxml, embedded labels, table is SHEETNAME)
WHERE PRICE_FIELD > '15';
Hope it helps